The cutting arrangement for a motor-driven chain saw usually comprises a saw chain, a guide bar for the saw chair and a sprocket drive wheel which is driven by the motor shaft of the chain saw. The guide bar has one or more elongated slots for receiving attachment bolts with which the guide bar is attached to the housing of the chain saw. These parts are often individually present whereby the assembly of the cutting arrangement on the housing of the chain saw is complex. First the sprocket drive wheel is pushed onto the motor shaft or a collar of a coupling and the guide bar is pushed onto attachment bolts of the chain saw housing. Thereafter, the chain is mounted and a cover covering the sprocket drive wheel is fixed to the chain saw housing with nuts which threadably engage the attachment bolts. Thereafter, the saw chain is tensioned and then the nuts are tightened on the attachment bolts in order to securely clamp the guide bar to the housing.
It is also known to preassemble parts of the cutting arrangement as a component during manufacture in order to facilitate this assembly work. The component can then be mounted on the housing of a chain saw configured in a suitable manner.
One such cutting arrangement is disclosed in U.S. Pat. No. 2,992,660. This cutting arrangement includes two mounting plates in addition to the guide bar, sprocket drive wheel and the mounted saw chain. The two assembly plates are mounted on both sides of the guide bar and, together with the guide bar, are mounted on the attachment bolts of the chain saw housing. In the preassembled component, the sprocket drive wheel is disposed either between two side plates of the three-part guide bar or between two cover washers having contours to which the guide bar is adapted. The chain can be tensioned by means of a saw chain tensioning device after mounting the component. The saw chain tensioning device comprises an adjusting screw seated in the saw chain housing with the head of this screw extending into a cutout of the inner mounting plate. In this way, the guide bar can be displaced relative to the sprocket drive wheel mounted on the motor shaft. The preassembled component is held together only by the saw chain which is not yet tensioned to its operational length but must nonetheless be so short that the parts of the component do not fall apart. Therefore, the saw chain can not simply be removed and exchanged on the component itself nor even after the component is mounted on the chain saw. This capability of removing and exchanging the saw chain is desirable because of wear and is also possible on conventional cutting arrangements which are not preassembled.
U.S. Pat. No. 4,316,327 discloses a similar cutting arrangement configured as a preassembled component. Here, the sprocket drive wheel is disposed in a chamber which is defined by bent-over sections of the two side plates of the three-part guide bar. An adjusting screw is mounted on the end of the guide bar for tensioning the saw chain. The adjusting screw engages in a bushing of the chain saw which is fixed on the housing. With this configuration too, the continuous saw chain cannot be removed from the guide bar and the sprocket drive wheel. The removal and also the threading of the saw chain is only possible when the saw chain is open and, for this purpose, one of the chain links must be removed and then later connected to another chain link.